Obturator



June 28, 1960 J GMMAN, JR 2,942,525

OBTURATOR Filed lay :51, 1945 INVENTOR v JOSEPH L. GILLMAN, JR.

BYMLW,

ATTORNEY H 2,942,525 I P f 'r f rlr v 2,942,525 oBTUnAibR manr. militiamen, pared States Navy Filed May 31, 1945, Ser. No. 596,931 1' (or. 8946 This invention relates to an obturator ornzasket, and

more particularly-to, a stableunitary gas checkpad for use inconnection with breech loading ordnance or other equipment utilizing high fluid pressures. 3 Previously, it has been common'practice to form ob- 'turators or gas check pads of a plurality or mass of heat resistant discs or fibers of asbestos variously oriented, impregnated or bound with vegetable, mineral or animal oils, fats or waxes, natural or processed, and the combined mass jacketed with metal gauze or fiber cloth. However, practice has proven these pads to have relatively poor durability, particularly under conditions of prolonged or rapid fire, due to a decrease in thickness of the pad brought about by the exudation of the impregnating or binding material or due to a rupture of the gasket by the steel gas check rings.

The primary object of this invention is to provide an unjacketed unitary obturator or gasket which embodies the well-known desirable characteristics such as, resilience, high tensile strength, resistance to abrasion, resistance to the action of oil and water, chemical stability and freedom from exudation or diminution in volume at high and low temperatures and at high and low pressures, in which the lateral or diametrical thermal coefficient of expansion is approximately that of the material enduring the pressure against which it seals.

An obturator or gasket made in accordance with this invention comprises multiple, transverse layers of a flexible fabric having a high tensile strength and low coeificient of thermal expansion, and a thermally stable rubber-like material, which impregnates and coats the fabric and bonds the layers together into a unitary structure. In a preferred form, the obturator or gas check pad is constructed of a series of chloroprene (neoprene) i-mpregnated and covered glass cloth discs of suitable diameters set one upon the other, molded under pressure, and cured with heat in steel molds to produce a completely bonded unit of a pre-designed size and shape.

A further explanation appears in the specification to follow, accompanied by the drawing in which:

Figure 1 is a cross-sectional view of the obturator interposed between a mushroom and a breech plug of a breech mechanism.

Figure 2 is a cross-sectional view of part of the bonded gas check pad.

Figure 3 is a perspective view, partly in cross-section, of a neoprene composition impregnated and coated glass cloth disc.

Referring to the drawing, Figure 1, A represents the gun, B the breech plug, C the mushroom retained in position by means of nut D which is attached to the mushroom stem and seated against spring E. The purpose of the spring is to resiliently position the mushroom against the obturator and forward gas check ring thereby permitting a variation in the longitudinal thickness of the obturator. The mushroom and stem are provided with a passage G through which the charge in the chamber F is fired in any suitable manner.

2 The obturator is interposed between the conventional mushroom and the breech .plug in such a way as to transmit theY'firirig load from the mushroom to the breech plug, and 'is thereby distended laterally. to provide a gas jsea'l atthe Fgas icheckseat H and at the rear base of the mushroom without interfering with the operation of the breech mechanism. g H

Thefobturatorltl, as shown, is in the form of an annulus through which the mushroom stem may extend,

the obturator having its outer surface 11 heveledto fit closely against the gas check seat H. The rear face 12 is flat andfits'clos'ely against the'front endof the breech plug B, while the forward face 13 of the obturator is a conical form to receive the base ofthemushroom seat. At its outer edges, the obturator is beveled, as shown at 14 and 1;4 A,to provide annular recesses at the ends of "the obturatorfor receiving suitable gas check rings, (not shown); ifsuch rings are desired.

,The'obturatorl comprises a plurality of laminations of afiexible, plastic-coated, material having a high tensile strength and a low diametrical coefiicient of thermal expansion. More particularly, each lamination 15 as shown in Figure 3, includes a layer of fiber glass cloth, or the like, having strands 16 of high tensile strength and low thermal coefficient of expansion extending generally transversely to the obturator, (that is, laterally with respect to the mushroom stem). The fiber strands 16 are coated and impregnated with a plastic material 17 which has rubber-like qualities, such as a neoprene composition. In the preferred construction, each strand 16 is made up a plurality of fibers, so that when the neoprene composition 17 is applied to the glass cloth the strands themselves are impregnated, bonded and coated by the neoprene composition which extends continuously over the two faces of the cloth and from face to face through the interstices of the fabric.

The luminations 15 are superimposed and molded together under pressure and heat to produce a completely bonded unit of the desired form. -It will be understood that the several laminations 15 may be of varying diameters, as shown, to provide the obturator with the desired shape.

With the new construction, the obturator is extremely resistant to transverse or lateral expansion under heat and its resistance in this respect is much greater than its resistance to longitudinal expansion. This is so because the transverse strands 16, being of 'high tensile strength and low thermal coefiicient of expansion, prevent any substantial transverse expansion of the laminations 15. The spaced layers of glass cloth 16 serve to reinforce or bind the neoprene composition 17 and because of their intimate association with the neoprene composition act to resist to a high degree any tendency for the obturator to expand transversely to a greater extent than the gun itself and thereby cause binding against the gas check seat H, or upon decreasing temperatures to shrink more than the gun and hence fail to form a gas seal. As pointed out above, the obturator 10 has less resistance to longitudinal expansion than to lateral or transverse expansion, because of the disposition of strands 16. On the other hand, any tendency of the obturator to expand longitudinally is accommodated by the spring E.

The new obturator is extremely resistant to wear, is resilient and flexible so that it can readily adapt itself to service requirements, is impervious to oil and water, and may be easily molded.

Tests conducted on an obturator made in accordance with the specification appurtenant to this invention disclosed that in the course of a 355 F. change in temperature, the thickness varied .066"; the diameter varying .013". In other words, the diametrical thermal coeflicient is equal to .0000051 inch per inch per degree Fahrenheit, which is similar to the diametrical thermal coefiicient of the gun. The thickness coeflicient is equal to .00016 inch per inch per degree Fahrenheit.

Maximum temperature and oil immersion tests have proven similarly satisfactory.

It' will be apparent that variations in the thermal coetficient of expansion may be efiected by using different materials in the fabric 16 or the bonding 17, or both, or by varying the ratio of the total fabric thickness to the total bonding thickness. 7

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes withoutthe payment of any royalties'thereon or therefor.

Having thus described my invention in the foregoing specification, I claim:

Ina breech mechanism for closing and sealing the chamber of a gun having a gas-check seat formed of a surface of revolution with predetermined thermal coetncient of expansion, a substantially cylindrical composite pad having an outer peripheral surface adapted to engage said seat throughout its inner periphery, a breech plug having a plane backing surface immediately adjacent said pad, a mushroom positioned on the sidl of said pad opposite said breech plug with a conformin; surface confronting the forwardly facing lateral surfac of said pad, said mushroom having limited freedom 0 movement axially of said seat for transmitting fluid pres sure in said chamber throughout the lateral surface 0 said pad, said pad being comprised of alternate bondel layers of resilient and fibrous material wherein said lay ers are positioned normal to the direction of movemer of said mushroom whereby said resilient material wii obturate between the layers of fibrous materialto engag the peripheral surface of said seat when said pad is con pressed between said breech plug and said mushroor by the application of fluid pressure to said mushroom.

References Cited in the file of this patent UNITED STATES PATENTS 822,644 Yarnell June 5, 19( 1,186,266 Asbury June 6', 19]

2,132,702 Simpson 'oct. 11, 192 2,360,830 Denman Oct. 24, 194

V FOREIGNPATENTS 844,748 France of 195 

